casting fixture

Abstract

Casting device (100) for a hot runner casting process, comprising: - a mold cavity (101), wherein the mold cavity (101) has at least two inlet openings, and - at least two at least partially heatable casting channels (102) which extend from a cavity (200) to the inlet openings and connect the cavity (200) with the inlet openings, characterized in that the cross-sectional area of ​​each of the at least two casting channels (102) in an end region facing the respective inlet opening is more than 30% smaller than the cross-sectional area in an end region facing the cavity (200), and that the cross-sectional area of ​​each of the at least two casting channels (102) decreases continuously in the direction from the end region facing the cavity (200) to the end region facing the respective inlet opening.

Description

[0001] The present invention relates to a casting device for a hot runner casting process according to the preamble of claim 1.

[0002] Casting devices with a mold cavity having inlet openings for sprues, wherein the sprues connect the inlet openings to a cavity, are known from the prior art. Such a casting device is known from DE 10 2008 052 062 A1. EP 0 976 475 A1 describes a casting device used for die casting that does not have heatable sprues.

[0003] In the hot runner casting process, a so-called sprue is created during the production of a component. In state-of-the-art hot runner casting fixtures, the sprue point is located within the component, necessitating complex mechanical post-processing to maintain the required dimensions. Furthermore, the sprue point located within the component can represent a weak point under mechanical stress. The hot runner casting process is primarily used for manufacturing components from metals or alloys. For example, aluminum or magnesium components can be produced using this method.

[0004] In the die-casting device according to EP 0 976 475 A1, the sprue is located outside the component being manufactured and is separated from the component after the casting process. This results in material loss, which increases production costs.

[0005] EP 0 976 475 A1 specifies that the cross-sectional area should be constant along the entire length of the casting channel. This is intended to include changes in the cross-sectional area of ​​up to 30%.

[0006] For the state of the art, reference is also made to DE 10 2008 052 062 A1, concerning a method for manufacturing a frame-like structural component, and to DE 10 2006 002 341 A1, concerning an injection molding tool.

[0007] In contrast to the prior art, the invention is based on the objective of creating a casting device for a hot runner casting process and such a hot runner casting process that enables a simpler separation of the sprue from the component, while at the same time resulting in less material loss.

[0008] According to claim 1, the cross-sectional area of ​​each of the at least two casting channels in an end region facing the respective inlet opening is more than 30% smaller than the cross-sectional area in an end region facing the cavity. The cross-sectional area of ​​each of the at least two casting channels in an end region facing the respective inlet opening can also be more than 50% or even more than 60% smaller than the cross-sectional area in an end region facing the cavity.

[0009] The relatively large decrease in cross-sectional area from the cavity towards the inlet openings means that the sprue, located in the end region facing the respective inlet opening, also has a smaller cross-sectional area, making it easier to separate from the component, for example by punching. The smaller cross-sectional area also results in less material loss.

[0010] Another advantage of the relatively small cross-sectional area is that microporosities in the component are reduced or even prevented, and a homogeneous flow is achieved.

[0011] The end region facing the respective inlet opening is understood here to be the area extending from the center of the respective casting channel to the end of the casting channel adjoining the inlet opening. The end region facing the cavity is understood here to be the area extending from the center of the respective casting channel to the end of the casting channel adjoining the cavity. In other words, the two end regions are located opposite each other at different ends of the casting channel. The casting channel extends longitudinally from the end region facing the cavity to the end region facing the inlet opening.

[0012] A sprue can consist of two parts. The first part can be heated and connect directly to the cavity, which may also be heated. The second part of the sprue can connect directly to the first part and be permanently attached to the mold cavity.

[0013] According to one embodiment of the invention, the number of sprues in the end regions facing the inlet openings can be at least twice as large as in the end regions facing the cavity. In other words, the sprues branch in the end regions facing the inlet openings. A sprue can branch into two or more sprues. The branching can, for example, be located in the second part of the sprue.

[0014] Such a branching design is particularly advantageous for a smoother material flow. The branching allows the cross-sectional area of ​​a single inlet opening to be significantly reduced, as twice the number of inlet openings are available for the material flow. This reduces turbulence within the material flow.

[0015] In such a case, the sum of the cross-sectional areas of the casting channels in the end regions facing the inlet openings can be more than 30% smaller than the sum of the cross-sectional areas in the end regions facing the cavity. In particular, the sum of the cross-sectional areas of the casting channels in the end regions facing the inlet openings can be more than 50% or even more than 60% smaller than the sum of the cross-sectional areas in the end regions facing the cavity.

[0016] Although the number of casting channels may increase due to the bifurcation, the sum of the cross-sectional area values ​​may decrease.

[0017] According to claim 1, it is further provided that the cross-sectional area of ​​each of the at least two casting channels decreases continuously in the direction from the end region facing the cavity to the end region facing the respective inlet opening. This is also particularly advantageous for a particularly homogeneous flow behavior of the material in the casting channel with very little turbulence.

[0018] According to one embodiment of the invention, the cross-section of the casting channels in the end region facing the respective inlet opening can have a square, elliptical, or oval shape. Either the cross-section of the entire casting channel can be square, elliptical, or oval, or only the cross-section of the casting channel in the end region facing the respective inlet opening.

[0019] It is also possible that the cross-sectional area of ​​the casting channel changes continuously from a round shape in the area directly adjacent to the cavity to an angular, elliptical, or oval shape in the area directly adjacent to the inlet opening. This, in turn, is particularly advantageous for a highly homogeneous material flow.

[0020] The angular, elliptical, or oval cross-section of the sprue near the inlet opening of the mold cavity results in a smaller plug, which also contributes to material loss. The plug forms during the casting process in the area where the sprue is no longer heated. The material cooling there cools from the outside in. With a round cross-section, the inner area is relatively far from the already cooling outer area. Therefore, solidification in the inner area occurs considerably later than solidification on the outside. Among other things, this time difference determines the length of the plug. The greater the time difference, the longer the plug. With an angular, oval, or elliptical cross-section, this time difference is smaller than with a round cross-section. Consequently, the length of the plug is also shorter, resulting in less material loss.Furthermore, a square, elliptical or oval shape is advantageous in order to make it particularly easy to separate the sprue from the component, for example by punching.

[0021] According to one embodiment of the invention, the device can include means for compensating for thermal expansion of the casting channels in a longitudinal direction. The casting channels are heatable and preferably made of a metal. When they are heated and / or when hot casting material, such as liquid aluminum or magnesium, flows through them, they expand—primarily in their longitudinal direction. This thermal expansion can lead to stresses in the device. Compensating for the thermal expansion is therefore advantageous in order to avoid such stresses.

[0022] Thermal expansion can be compensated for, for example, by wedge-shaped elements on which a support for the sprues and / or the cavity is mounted. These wedge-shaped elements have a thicker end and a thinner end. Between the thinner and thicker ends, the cross-sectional area of ​​the wedge-shaped elements increases continuously. When the sprues are heated and expand, the wedge-shaped elements can be shifted so that the support for the sprues and / or the cavity moves away from the mold cavity, thus compensating for the thermal expansion of the sprues. The same principle applies in reverse when the sprues cool.

[0023] According to one embodiment of the invention, each of the sprues can have a recess. Furthermore, collecting means can be arranged in the region of the recess in each of the sprues. The collecting means can be designed to catch a solid body exiting through the respective recess. The solid body can, for example, be a plug, as described above. Such a plug forms where the sprue is no longer heated. Therefore, the recess is advantageously arranged where the sprue can no longer be heated. The plug thus remains in the sprue after a casting process at the transition between the first and second parts of the sprue. The recess and the collecting means are provided to prevent this plug from interfering with the casting process or even clogging the sprue during the next casting process.In the collection devices, the plug does not impair the flow behavior of the casting material.

[0024] According to one embodiment of the invention, each of the sprues can have an undercut in the end region facing the respective inlet opening. The undercut is preferably located in the second, unheated section of the sprue. The undercut is designed so that the sprue remains on the ejector side of the mold cavity when the mold cavity is opened. The mold cavity has a nozzle side and an ejector side. The nozzle side is the side of the mold cavity where the inlet openings are located. When the mold cavity is opened, the ejector side is at least partially separated from the nozzle side. The undercut is designed such that, when the mold cavity opens, the sprue breaks off in such a way that it is located on the ejector side. This ensures that no solid material remains on the nozzle side or in the sprue. Any material remaining there would interfere with subsequent casting processes.Since all the solidified material is located on the ejector side, it is expelled from the mold cavity along with the component, and the mold cavity can be used directly for another casting process. Therefore, the collection devices described above are not required.

[0025] During cooling, the cast material shrinks, allowing the component, including the sprue, to be ejected from the mold cavity. Therefore, the undercut dimensions are preferably chosen so that the undercut does not prevent ejection when the material shrinks during cooling.

[0026] According to one embodiment of the invention, the casting channels extend obliquely outwards from the cavity. This includes, for example, a Y-shaped configuration of two casting channels. An oblique outwards extension is thus understood to encompass all directions in which the casting channels extend even partially outwards from the cavity. Such a geometry is particularly advantageous for a short material flow path through the casting channels. In addition, the thermal expansion of the casting channels can be compensated for very efficiently.

[0027] According to one embodiment of the invention, the device comprises support elements designed to support the casting channels and the cavity. The means for compensating for thermal expansion can, for example, be arranged between two parts of the support elements, allowing the distance between these two parts to be adjusted. This compensates for the thermal expansion of the casting channels. One part of the support elements can, for example, be designed as a solid metal block. A high weight of the support elements ensures high stability of the device, particularly during the casting process.

[0028] In another aspect, the invention relates to a hot runner casting process for manufacturing a component using a casting device according to one embodiment of the invention. The shape of the manufactured component is defined by the mold cavity of the casting device. First, a metal or alloy, which has been heated to at least the necessary thixotropic or semi-solid state, is injected into the mold cavity through the cavity, the casting channels, and the inlet openings. For example, aluminum or magnesium alloys, depending on the alloying elements, can be injected at temperatures between 550°C and 660°C. Within this temperature range, aluminum or magnesium alloys exhibit thixotropic properties, depending on the alloying elements. It is also possible to inject other metals, such as zinc.

[0029] After the injection process, the material cools down, transitioning from a liquid to a solid phase. The mold cavity is then opened, the component produced from the material is removed, and the sprue, which is bonded to the component due to the manufacturing process, is punched off.

[0030] It can also be provided that the thermal expansion of the casting channels is compensated for before and during the injection process and during cooling. This can be achieved, for example, by a wedge guide as described above.

[0031] Further features and advantages of the present invention will become clear with reference to the following description of preferred embodiments and the accompanying figures. The same reference numerals are used for identical or similar features or components. These figures show Fig. 1 a schematic perspective view of a casting device according to an embodiment of the invention; Fig. 2 a schematic perspective view of parts of a casting device according to an embodiment of the invention; Fig. 3 a schematic partial view of a section from Fig. 2; Fig. 4 A and B schematic representations of the functioning of means for compensating for thermal expansion of the casting channels; and Fig. 5 A to C schematic representations of an undercut in an end area of ​​a casting channel.

[0032] In Fig. Figure 1 shows a casting device 100 according to an embodiment of the invention. The casting device 100 comprises a mold cavity 101, which defines the shape of a component to be produced. The mold cavity 101 is connected to casting channels 102 via inlet openings (not shown). Liquid material can be introduced into the mold cavity 101 through the casting channels 102. The casting channels 102 are partially surrounded by heating elements 104, allowing them to be heated in this partial area. The casting device 100 is also connected to supply lines 106. Liquid material can be introduced into the casting device 100 via these supply lines 106.

[0033] Furthermore, the casting device 100 includes means 108 for compensating for thermal expansion of the casting channels 102. When hot material flows through the casting channels 102, or when the casting channels 102 are heated by the heating means 104, they expand—primarily in their longitudinal direction, which is parallel to the flow direction of the material flowing through the casting channels 102. This expansion could lead to stresses within the casting device 100.

[0034] The means 108 for compensating for the thermal expansion of the casting channels 102 are arranged between a first part 110 of support means and a second part 112 of support means. Furthermore, the means 108 are wedge-shaped. When the wedge-shaped means 108 are moved between the two parts 110 and 112 of the support means, the distance between the parts 110 and 112 changes due to the changing thickness of the wedge-shaped means 108 in the area between the two parts 110 and 112. If a relatively thick area of ​​the wedge-shaped means 108 is arranged between the two parts 110 and 112, the distance between the two parts 110 and 112 is relatively large. Conversely, if a relatively thin area of ​​the wedge-shaped means 108 is arranged between the two parts 110 and 112, the distance between them is relatively large.

[0035] By changing the distance between the two parts 110 and 112, changes in the length of the casting channels 102 can be compensated for, thus avoiding stresses within the casting device 100 due to changes in the length of the casting channels 102.

[0036] The casting device 100 is particularly advantageous because a sprue (in Fig. (1 not shown) is not located within the component being manufactured. The sprue can be easily removed from the manufactured component after the casting process, for example by punching.

[0037] In Fig. Figure 2 shows that the two sprues 102 are connected to a cavity 200. The liquid material enters the sprues via the cavity 200. This liquid material can be, for example, molten metal or a molten alloy. The sprues extend outwards from the cavity 200 towards the mold cavity 101.

[0038] It should be noted that in the embodiment of the casting device 100 shown here, only two casting channels 102 are provided. A casting device with more than two casting channels, which also extend outwards away from the cavity 200, can be realized, for example, by connecting the cavity 200 to two further sides of the mold cavity 101 with two additional casting channels.

[0039] The cross-sectional area of ​​the sprues 102 decreases by more than 30% from the cavity 200 to the inlet openings of the mold cavity 101. Preferably, the sum of the cross-sectional areas of the sprues 102 in the end region near the inlet openings of the mold cavity 101 is 30% to 50% of the sum of the cross-sectional areas of the sprues 102 in the end region near the cavity 200. This reduction in cross-sectional area results in particularly homogeneous flow behavior of the material. Furthermore, relatively little material is lost during the stamping of the sprue. In addition, the sprue can be more easily separated from the manufactured component due to its smaller cross-sectional area.

[0040] Furthermore, the cross-sectional shape of the casting channels 102 changes. In the area near the cavity 200, the casting channels 102 have a round cross-sectional area, whereas in the area near the inlet openings of the mold cavity 101, they have a rectangular cross-sectional area. They can also have an oval or elliptical cross-sectional area instead of a rectangular one.

[0041] Furthermore, in Fig. Figure 2 shows a fork 202 in one end region of each sprue 102. This fork 202 results in the number of sprues 102 in the region near the cavity 200 being half the number of sprues 102 in the region near the inlet openings of the mold cavity 101.

[0042] The in Fig. Section 2, marked with an A, is shown in detail in Fig. Figure 3 shows the fork 202 particularly clearly. This fork results in the liquid material being injected into the mold cavity 101 through twice as many inlet openings. This, in turn, leads to a particularly homogeneous material flow and prevents microporosity of the material.

[0043] In Fig. Figure 3 also shows collecting devices 300. These serve to catch any plug that forms when the material cools in the unheated area of ​​the casting channel 102 and prevents it from entering the mold cavity 101.

[0044] Through the above with reference to Fig. The change in cross-sectional area from round to rectangular along the casting channels 102 mentioned above results in a shorter plug length. With a rectangular cross-section, the inner part of the plug cools faster than with a round cross-section. Therefore, the time difference between the cooling of the outer area and the cooling of the inner area is smaller, which also reduces the plug length.

[0045] In the Fig. 4A and Fig. Figure 4B illustrates the function of the wedge-shaped means 108 for compensating for the thermal expansion of the casting channels 102. For clarity, the first part 110 of the support means is not shown. Fig. 4A The second part 112 of the support means rests on a relatively thin section of the wedge-shaped means 108. If the casting channel 102 expands – due to heating by means of the heating means 104 or due to the flow of hot material – the wedge-shaped means 108 can be moved so that the second part 112 of the support means rests on a thicker section of the wedge-shaped means 108. The wedge-shaped means 108 always rest on the section that is in the Fig. 4A and Fig. 4B, the first part 110 of the support means not shown.

[0046] In Fig. Figure 4B shows the situation when the second part 112 of the support means rests on a thicker area of ​​the wedge-shaped means 108. There is now a gap between the sprue 102 and the mold cavity 101, since in Fig. Figure 4B does not show the thermal expansion of the casting channel 102 to illustrate the effect. The raising of the casting channel 102 by shifting the wedge-shaped means 108 can be coordinated with the thermal expansion of the casting channel 102 in such a way that thermal stresses within the casting device 100 are reduced or even completely avoided.

[0047] The wedge-shaped means 108 can also be used in reverse to compensate for a shortening of the casting channels during cooling.

[0048] Fig. Figure 5A shows a casting channel 102. A sectional view along the in Fig. The section line AA shown in 5A is in Fig. Figure 5B shows part 500 of the sprue. The sprue is located outside the component to be manufactured. Fig. Figure 5B shows that an undercut 502 is arranged on the ejector side 504 of the mold cavity 101. The part 500 of the gate fills the undercut so that when the mold cavity 101 opens, the ejector side 504 is ejected along the ejector side 504 of the mold cavity 101. Fig. The line 508 shown in Figure 5B, which separates the ejector side 504 from the nozzle side 506, ensures that the sprue remains on the ejector side 504. The undercut 502 thus guarantees that the sprue always remains on the ejector side 504. If the sprue were to remain on the nozzle side 506, this would hinder the production of another component with the casting device 100.

[0049] When using the undercut 502, collecting media 300, such as those found in Fig. The numbers shown in point 3 are omitted.

[0050] In Fig.Figure 5C shows part 500 of the sprue after cooling. Due to the low temperature, shrinkage has occurred, so that part 500 of the sprue no longer fills the undercut 502. Instead, a cavity 510 is present. This allows the component, including the sprue, to be ejected from the ejector side 504 of the mold cavity 101. Due to the temperature-induced shrinkage, the undercut 502 does not obstruct ejection. It is therefore important to ensure that the dimensions of the undercut are chosen so that the shrinkage is sufficient to allow the component, including the sprue, to be ejected from the ejector side 504 of the mold cavity 101. Reference symbol list 100 casting devices 101 Mold cavity 102 casting channels 104 Heating materials 106 Supply line 108 methods for compensating for thermal expansion 110 first part of support equipment 112 second part of shoring equipment 200 cavity 202 Junction 300 collection containers 500 part of the sprue 502 Undercut 504 Ejector side 506 Nozzle side Line 508 510 cavity A section

Claims

[1] Casting device (100) for a hot runner casting process, comprising: - a mold cavity (101), wherein the mold cavity (101) has at least two inlet openings, and - at least two at least partially heated casting channels (102) which extend from a cavity (200) to the inlet openings and connect the cavity (200) with the inlet openings, characterized by , that the cross-sectional area of ​​each of the at least two casting channels (102) in an end region facing the respective inlet opening is more than 30% smaller than the cross-sectional area in an end region facing the cavity (200), and that the cross-sectional area of ​​each of the at least two casting channels (102) decreases continuously in the direction from the end region facing the cavity (200) to the end region facing the respective inlet opening. [2] Casting device (100) according to claim 1, characterized by, that in the end regions of the casting channels (102) facing the inlet openings the number of casting channels (102) is at least twice as large as in the end regions of the casting channels (102) facing the cavity (200). [3] Casting device (100) according to any one of the preceding claims, characterized by , that the cross-section of the casting channels (102) in the end area facing the respective inlet opening has a square, elliptical or oval shape. [4] Casting device (100) according to any one of the preceding claims, characterized by , that the device includes means (108) for compensating for thermal expansion of the casting channels (102) in a longitudinal direction. [5] Casting device (100) according to any one of the preceding claims, characterized by, that each of the casting channels (102) has a recess, and that collecting means (300) are arranged in the area of ​​the recess of each of the casting channels (102), wherein the collecting means (300) are designed to catch a solid body exiting the casting channel (102) through the respective recess. [6] Casting device (100) according to any one of claims 1 to 4, characterized by , that each of the casting channels (102) has an undercut (502) in the end area facing the respective inlet opening. [7] Casting device (100) according to any one of the preceding claims, characterized by that the casting channels (102) extend obliquely outwards away from the cavity (200). [8] Casting device (100) according to any one of the preceding claims, characterized by , that the device has support means (110; 112) wherein the support means (110; 112) are designed to support the casting channels (102) and the cavity (200). [9] Hot runner casting method for producing a component using a casting device (100) according to one of the preceding claims, wherein the shape of the component is defined by the mold cavity (101), characterized by that the procedure includes the following steps: a. Providing a casting device (100) according to one of the preceding claims; b. Injecting a liquid and / or viscous material at a temperature above 200°C through the cavity (200), the at least partially heated casting channels (102) and the inlet openings into the mold cavity (101); c. Cooling of the material and associated d. Transformation of the material from the liquid phase to the solid phase; e. Opening the mold cavity (101) and f. Stamping out a sprue that is materially bonded to the component.

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